The proposed research involves studies of the mechanisms of biochemical oxidation and reduction reactions. Previous work by the principal investigator and his coworkers using model systems has shown that the oxidation and reduction of functionalities found in biologically important chemicals can proceed by free-radical mechanism. Specifically, alcohol, aldehyde and amine functions are oxidized in free-radical chain reactions involving either hydrogen-atom or electron transfer from the substrate-derived radical to oxidizing agents such as peroxides. Employing our background in the free-radical chemistry of these systems, we propose both to extend our research to the real biochemicals and to initiate investigations in new areas in which free-radical chemistry may be important. Specifically we proposed to determine the kinetic rate laws of oxidation and reduction reactions of certain of the biochemical cofactors found in electron transport processes, namely the pyridine nucleotides, riboflavin and quinones, as well as ascorbic acid, oxygen. Kinetic studies of the type proposed will indicate if participation of the cofactor in a free-radical chain reaction actually can occur. Research is proposed in the areas of enzyme mechanism, particularly the reactions of peroxidase and catalase with peroxides. Examination of these systems is proposed in terms of the free-radical chemistry of hydrogen peroxide and paraphorin-complexed iron ions. Research is outlined both for model systems and the enzymes themselves and involves both chemical, kinetic and electrochemical studies. Investigations are proposed concerning certain aspects of the primary processes in photosynthesis, particularly the oxidation of water to molecular oxygen. A scheme involving manganese (III) and hydrated dehydroascorbic acid is proposed to account for this yet unexplained reaction in photosynthesis. Aspects of this work are related to proposed research in biological hydroxylation reactions.